1. Field of the Invention
The present invention relates to a honeycomb structured body.
2. Discussion of the Background
Conventionally, a honeycomb catalyst generally used for exhaust gas conversion of an automobile is manufactured by supporting a high specific surface area material such as active alumina and the like and a catalyst metal such as platinum and the like on a surface of a cordierite-based honeycomb structured body that has an integral structure and a low thermal expansion property. Moreover, an alkaline earth metal such as Ba and the like is supported thereon as a NOx occlusion agent, so as to be used for treating NOx in an atmosphere with excessive oxygen such as an atmosphere in a lean burn engine and a diesel engine.
Here, in order to improve the converting performance of the honeycomb catalyst, it is necessary to increase the possibility of contact between exhaust gases and the catalyst noble metal as well as the NOx occlusion agent. For this purpose, it is necessary for the support to have a higher specific surface area and for the noble metal to have a smaller grain size and to be dispersed in a high level. Therefore, many kinds of honeycomb structured bodies are proposed in which the cell shape, the cell density, the thickness of cell walls, and the like have been devised (for example, see JP-A 10-263416).
With respect to the honeycomb structured body made of a high specific surface area material, a honeycomb structured body that has been subjected to extrusion molding with inorganic fibers and an inorganic binder has been known (for example, see JP-A 5-213681). Moreover, in order to allow such a honeycomb structured body to have a large size, a structure in which honeycomb units are jointed to one another through an adhesion layer has been known, and honeycomb structured bodies with honeycomb units having a cross-sectional area of 200 cm2 or more have been proposed (for example, see DE 4341159).
The contents of JP-A 10-263416, JP-A 5-213681, and DE 4341159 are incorporated herein by reference in their entirety.